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Extensive use of LiFePO4 batteries will afford a lot of spent LiFePO4 batteries, which cannot be recycled properly by using traditional processes at present. If these spent LiFePO4 batteries are thrown away without recycling properly, it is not only a severe waste of valuable resources, but also leads to serious environmental pollution. In this paper, a completely green recycling process and a small scale model line are developed to recycle cathode powders from spent LiFePO4 batteries for the first time. Parts of LiFePO4 host particles in spent LiFePO4 batteries decompose to FePO4, Fe2O3, P2O5 and Li3PO4 after numerous charge–discharge cycles, resulting in poor electrochemical performance of freshly recycled cathode powders for Li-ion batteries. To repair decomposed LiFePO4 host particles, recycled cathode powders are heat-treated at different temperatures. After heat-treatment at high temperatures, especially at 650 °C, cathode powders are effectively recycled and can be reused for Li-ion batteries.

To recycle valuable resource and reduce environmental pollution, a green full-solid route is designed to resynthesize LiFePO4/C materials from spent lithium-ion batteries for the first time. With this full-solid route, a simple thermal treatment process is employed to purify and homogenize the recycled cathode materials. No waste acid or alkaline liquid is used, which can avoid the secondary environment pollution. Further, the effect of Li2CO3 content on the performances of regenerated LiFePO4/C materials is investigated in detail and LiFePO4/C materials with high purity and high tap density are resynthesized. Among these resynthesized LiFePO4/C materials, the one with Li2CO3 addition amount of 1.4 wt% displays excellent physical, chemical and electrochemical performances in half cell and full cell, meeting the reuse requirement for Li-ion batteries. These results indicate that this green full-solid route with simple-operation, easily large-scale preparation, low-cost and high added-value is a feasible and promising way to recycle scrapped cathodes and reuse them.

A green recycling process was designed and used to recycle spent LiCoO2 batteries, and the recycled LiCoO2 was regenerated after the solid state synthesis with Li2CO3. XRD results showed that the layered structure of LiCoO2 was repaired after regeneration. The physical and chemical properties (XRD, morphology, tap density, average particle size, specific surface areas and pH value) and electrochemical properties (discharge capacity, attenuation rate of capacity, plateau retention at 3.6 V and attenuation rate of plateau) of LiCoO2 after regeneration were tested in detail and compared with commercial LiCoO2. The test data show that the regenerated LiCoO2 at 900 °C can meet the commercial requirements for reuse.